The present invention relates generally to dynamoelectric machines, and, more particularly, to methods of making improved rotor structures which are hermetically sealed within an assembly such as a refrigeration compressor.
In refrigeration compressors of the hermetically sealed type, stators and rotors which comprise electric motor parts are mounted so as to operatively drive a shaft which is connected to a compressor mechanism. Such compressor mechanism may be of the reciprocating piston type as shown, for example, in Cheers U.S. Pat. No. 3,663,127 which issued May 16, 1972. On the other hand, such compressor units may be of the type known in the industry as rotary compressors. In many such compressors, the shaft itself is hollow and such an arrangement is illustrated in the above-referenced Cheers U.S. Pat. No. 3,663,127. An axially extending hole in the shaft may be utilized for numerous different functions. Typically, for example, the hole may be utilized to provide a passage through which lubricating oil may pass and thence be circulated from one end of the shaft to another. This type of arrangement is illustrated and discussed in some detail in the above-referenced Cheers patent. As will be understood by persons skilled in the art, rotors used in these types of applications usually are provided with rivets or other fastening means which are utilized to secure counterbalance weights. The counterbalance weights then provide the function of counterbalancing unbalances in the rotor structure per se, and/or unbalances associated with masses that are attached to the rotor shaft. One such mass may, for example, be a crankshaft and one or more pistons (along with connecting structure therefor) which are attached to the crankshaft. Counterbalance weights and methods of attaching the same are illustrated and described in McCroskey at al U.S. Pat. No. 3,965,382 which issued June 22, 1976 (as well as in the above-referenced Cheers patent).
Prior to the present invention, others have suggested and presumably used in commercial practice, shrouds which were attached to the top of the rivets or other fastening means that were provided to hold balance weights in place on the rotor structure. These shrouds, known by others prior to the present invention, were intended to give support to exceptionally heavy counterweights on the rotor. In addition, the shrouds that were suggested by others would serve an additional desirable function of deflecting refrigerant gas in the area of the shroud. It apparently has been concluded that it would be desirable to prevent any high pressure gas within the compressor unit from being directed axially downwardly along the rotor shaft.
Carter U.S. Pat. No. 2,875,694 which issued Mar. 3, 1959 illustrates an end closure plate disposed above the end of a hollow rotor shaft. Even though Carter relates to an art generally nonanalogous to the hermetically sealed refrigerator compressor art, a review of the structure shown by Carter will be helpful to an understanding of the relationships of parts that have been described hereinabove. Still other patents in nonanalogous arts are broadly addressed to methods of attaching counterweights. One such patent, for example, is McClendon U.S. Pat. No. 2,993,386 which is related to the nonanalogous art of mounting balance weights to motor vehicle brake drums.
Other patents of which I am aware that generally illustrate hermetically sealed refrigeration compressor motor parts are Smith U.S. Pat. No. 2,089,626 of Aug. 10, 1937; Hurst et al U.S. Pat. No. 3,584,980 of June 15, 1971; Heitchue U.S. Pat. No. 3,614,384 which issued Oct. 19, 1971; Leffers et al U.S. Pat. No. 3,664,461 which issued May 23, 1972; and Mitch U.S. Pat. No. 4,091,638 which issued May 30, 1978.
Of the above patents, the 1937 patent of Smith illustrates generally the type of apparatus referred to hereinabove (including balance weights). The Hurst et al patent clearly illustrates a piston type compressor utilizing a rotor shaft having oil pumping passages therein; and the Heitchue patent illustrates a piston type compressor having a piston attached to the upper end of the rotor shaft. The Leffers et al patent, on the other hand, describes in some detail the lubricating arrangements for hermetically sealed compressor motor parts; while the Mitch patent is concerned with cooling of hermetically sealed compressor motor parts. The Mitch patent is also of interest at least to the extent that it illustrates a cap member denoted by the numeral 72 in the Mitch patent which extends above the drive shaft of the compressor and seals off the shaft which is provided with oil passages.
As indicated hereinabove, prior to the present invention others have suggested the use of shrouds that would both structurally reinforce rotor structures having exceptionally heavy counterweights as a part thereof, and that would deflect gas in the area of the end of the rotor. Work performed by others utilizing such arrangements identified new problems associated with such shroud usage. More specifically, it was found that for one reason or another it might, on occasion, be desirable to disassemble the motor parts of a given compressor wherein a shroud had been utilized.
The actual assembly of motor parts in a compressor usually involves press fitting a rotor body onto a shaft; and disassembly of such parts requires that the end of the shaft be accessible for tools and fixtures which are to be utilized to press the shaft back out of the rotor. However, when shrouds are provided at the end of the shaft, the shaft end becomes inaccessible. As a solution to this problem, others have suggested that the shroud be provided with a hole in the center thereof which would permit access to the end of the rotor shaft in the event that it was desired to press the shaft out of the rotor. This suggested solution however was not fully satisfactory for the reason that gases within the compressor would then have access to the end of the shaft and the interior of the rotor through the centrally disposed opening in the shroud.
Still another suggestion or remedy for correcting the exposed shaft and shaft accessibility problems involved the suggestion of providing spring loaded closure plugs which would be snapped into a hole in the center of a rotor shroud. It has been thought, however, that such an arrangement would be unsatisfactory since the spring loaded plugs could contribute to vibration, and/or might in fact be dislodged during motor operation. To simplify the disclosure that is presented herein, and which was conceived against the background of all of the preceding description; it is now noted that the entire disclosures of all of the above cited patents are incorporated herein by reference--with the exception of any patents that have been specifically indicated to be directed to nonanalogous subject matter.
It should now be understood that it would be desirable to provide a method of manufacturing a rotor for a hermetically sealed compressor wherein the rotor includes a shroud disposed to cover the end of a shaft subsequently assembled with the rotor. More specifically, it would be desirable that such shroud be closed in the central portion thereof to prevent exposure of the end of the shaft to gases in that area. In addition, it would be desirable that the shroud be devised such that the rotor could be disassembled from the shaft by pressing against the end of the shaft under the shroud without destroying the usefulness of the rotor in a subsequently reassembled compressor. Moreover, it would be desirable to provide methods of making new and improved rotor constructions whereby the rotor structure, including the shroud supplied therewith, would be completely reusable in a reassembled compressor environment with the shroud protecting the end of the shaft from gases being directed thereon and all without requiring the use of auxiliary caps or plugs.
Accordingly, it is an object of the present invention to provide methods of making new and improved rotor structures so that the rotor structures are usable in a sealed compressor environment wherein a shroud on the end of the rotor will be effective to deflect gases from the end of the rotor shaft, and yet wherein such structure may be readily separated from a press fit shaft without destroying the rotor, shaft, or shroud; and yet wherein the rotor and shroud may be reassembled on the same shaft or a different shaft with the shroud structure performing the same desired deflection function in the subsequently reassembled environment.
Another object of the present invention is to provide a new and improved method of salvaging and re-using shrouded rotors in compressor assemblies; and improved rotor assemblies particularly adapted for use in such methods.